Photoresist composition

Abstract: A negative or positive photoresist composition which comprises an alkali soluble resin containing at least one resin selected from the group consisting of a partially alkyletherified polyvinylphenol and a partially alkyletherified hydrogenated polyvinylphenol, a photo-induced acid precursor containing at least a kind of sulfonic acid ester of N-hydroxyimide compounds and a crosslinking agent or dissolution inhibitor, and this photoresist composition is excellent in various properties such as heat resistance, film thickness retention, coating property, profile and the like, and further exhibits high sensitivity and high resolution when far ultraviolet rays including excimer lasers are used as the light source. It also hardly cause a scam during the developing process.

Description: The present invention relates to a resist compositions particularly suitable for use in lithography using far ultraviolet rays including excimer laser. Recently, with an improvement in the integration level of integrated circuits, formation of lithographic pattern of submicron order is required. Particularly, excimer laser lithography using excimer laser as its light source is becoming more important, because it makes it possible to produce 64 and 256 M DRAMs. As a result of such a change of the light source used, the following properties are demanded recently in addition to the hitherto required properties such as heat resistance, film thickness retention, profile, etc.: (1) high sensitivity to the light source mentioned above, (2) high resolution, In view of the above-mentioned state of art, so called chemical amplification type resists utilizing an acid catalyst and a chemical amplification effect has been proposed. Using this type of resist, an acid is generated from a photo-induced acid precursor upon irradiation with light. And a reaction utilizing the catalytic action of acid thus caused changes in the solubilities in the developer of the exposed parts and unexposed parts, and amplified the difference between the solubilities. As its result, a positive photoresist or negative photoresist is obtained. As an alkali-soluble resin in such chemical amplification type resists, polyvinylphenol has hitherto been widely used. The solubility of the polyvinylphenol in an alkaline developer, however, is too high, and due to the high solubility, a photoresist exhibiting sufficient sensitivity and sufficient resolution cannot be obtained. It is an object of the present invention to provide chemical amplification type negative photoresist compositions exhibiting excellent sensitivity and resolution while maintaining other favourable properties of usual resists such as heat resistance, film thickness retention, coatability, profile, etc. The present invention provides a chemical amplification type negative photoresist composition which comprises (A) an alkali soluble resin containing at least one resin selected from the group consisting of a partially alkyletherified polyvinylphenol (herein after denoted to as A1) and a partially alkyletherified hydrogenated polyvinylphenol (herein after denoted to as A2); (B) a photo-induced acid precursor containing at least a kind of sulfonic acid esters of N-hydroxyimide compounds; and (C) a cross-linking agent. Examples of the sulfonic acid esters of N-hydroxyimide compounds include an ester represented by the following formula (I): wherein R 1 is an optionally substituted arylene, alkylene or alkenylene group and R 2 is an optionally substituted alkyl or aryl group. Examples of the arylene group denoted by R 1 in the formula (I) include monocyclic and bicyclic arylene groups, among them phenylene or naphthylene are preferred. As preferred substituents on the arylene group, halogen atoms, nitro groups or acetylamino groups can be referred to. Examples of the alkylene groups denoted by R 1 in the formula (I) include straight chain and branched chain alkylene groups, among which those having 1 to 6 carbon atoms are preferable and particularly preferable are ethylene or propylene. As preferable substituents on the alkylene group, halogen atoms, lower alkoxy groups or monocyclic aryl groups can be referred to. Examples of the alkenylene groups denoted by R 1 in the formula (I) include those having 2 to 6 carbon atoms, among which vinylidene is preferable. As preferable substituent on the alkenylene group, monocyclic aryl groups can be referred to. Examples of the alkyl groups denoted by R 2 in the formula (I) include straight chain and branched chain alkyl groups, among which those having 1 to 8 carbon atoms are preferable. As preferable substituent on the alkyl group, lower alkoxy groups can be referred to. Examples of the aryl groups denoted by R 2 in the formula (I) include monocyclic and bicyclic aryl groups, among which monocyclic aryl groups are preferable. When R 2 is a substituted alkyl or aryl group, it is preferable that its substituent is not a fluorine atom. As examples of the sulfonic acid esters of N-hydroxyimide compounds, the following can be referred to: The esters represented by the formula (I) can be produced, for example, by reacting a cyclic N-hydroxyimide compound represented by the following formula (III): wherein R 1 is as defined above, and which can be produced according to a method described in, for example, G. F. Jaubert, Ber., 28 , 360 (1985), D. E. Ames et al., J. Chem. Soc., 3518 (1955) or M. A. Stolberg et al., J. Amer. Chem. Soc., 79 2615 (1957), etc., with a sulfonyl chloride represented by the formula R 2 -SO 2 Cl wherein R 2 is as defined above, under basic conditions according to a method, for example, described in L. Bauer et al., J. Org. Chem., 24 , 1293 (1959), etc. The esters represented by the formula (I) can be used either independently or in the form of a mixture of two or more. Resin A1 is preferably a partially alkyletherified poly(p-vinylphenol) which alkyletherification ratio is from 10 to 35 mole%. As the resin A2, preferable is that having an alkyletherification ratio being from 5 to 30 mole%. The mixing ratio of resin A1 and A2 is determined according to the situation where they are used. An alkali-soluble resin other than the resin A1 and A2 can be contained in the above-mentioned resin (A). Examples of the alkali-soluble resin other than the resin A1 and A2 include vinylphenol resins, isopropenylphenol resins, copolymers of vinylphenol and styrene (preferable molar ratio of the vinylphenol in the copolymer is 50% or more.), copolymers of isopropenylphenol and styrene (preferable molar ratio of the isopropenylphenol in the copolymer is 50% or more.), or hydrogenated polyvinylphenol. The mixing ratio of the alkali-soluble resin other than A1 and A2 to the resin A1 and A2 can be determined according to the situation where they are used, as long as the object of the present invention is attained. Examples of the alkylether include straight chain and branched chain alkylethers, among which those having 1 to 4 carbon atoms are preferable, and particularly preferable is methylether or ethylether. A preferable alkyletherification ratio of the resin A1 is from 15 to 22 mole% and that of the resin A2 is from 8 to 20 mole%. The resin A1 can be produced by reacting a polyvinylphenol with an alkyl halide according to a method described in, for example, G. N. Vyas et al., Org. Syntheses Coll. Vol. IV, 836 (1963), etc. The resin A2 can be produced by reacting a hydrogenated polyvinylphenol with an alkyl halide according to a method described in, for example, above-mentioned G. N. Vyas et al., etc. The hydrogenated polyvinylphenol can be produced by a hydrogenation of a polyvinylphenol according to a usual method. The alkali-soluble resins A1 and A2 usually have a weight average molecular weight of from 1,000 to 10,000 measured by GPC calculated as polystyrene, preferably from 1,500 to 8,000 and particularly preferably from 2,000 to 5,000. Examples of the cross-linking agent include the compounds having methylol groups or methylol-ether groups described in, for example, Japanese Patent Application No. 92-15009. As the preferable examples, the following can be referred to: The cross-linking agents having methylol groups or methylol-ether groups can be used either independently or in the form of a mixture of two or more. In the negative photo resist compositions, the mixing ratio of the ingredients is preferably as follows: alkali-soluble resin from 50 to 95 % by weight, cross-linking agent from 1 to 30 % by weight, photo induced acid precursor from 1 to 20 % by weight. To the negative photoresist compositions of the present invention, various additives conventionally used in this field of art, such as sensitizers, dyes, adhesion or improvers may be added, if desired. A photoresist solution is usually prepared by mixing the above-mentioned negative photoresist composition into a solvent so that the concentration of the composition in the total mixture comes to 10 to 50 % by weight. Examples of the solvents usable for this purpose include ethyl cellosolve acetate, methyl cellosolve acetate, ethyl cellosolve, methyl cellosolve, propyleneglycol monomethylether acetate, propyleneglycol monoethylether acetate, propyleneglycol monomethylether, propyleneglycol monoethylether, diethyleneglycol dimethylether, ethyl lactate, butyl acetate, ethyl pyruvate, 2-heptanone, cyclohexanone, methyl-isobutyl ketone, or xylene. These solvents can be used either independently or in combination of two or more. The positive photoresist compositions and the negative photoresist compositions of the present invention are excellent in various properties such as heat resistance, film thickness retention, coatability, profile and the like. They further exhibit high sensitivity and high resolution when far ultraviolet rays including excimer lasers are used as the light source. They also have the advantage that minute residue (scam) is hardly caused during the developing process, particularly when the alkali-soluble resin is A2. Accordingly, in the lithography using the above-mentioned light source, the resolution and the contrast can be remarkably improved and highly precise fine photoresist pattern can be formed. Next, the present invention will be explained in more detail with reference to the following examples. In the examples, parts are by weight, unless otherwise referred to. Referential Example 1 Into acetone, 10 g of polyvinylphenol (LYNCUR M; weight average molecular weight 4150; manufactured by Maruzen Petrochemical Co.) was dissolved, then 12.0 g of potassium carbonate and 3.38 g of ethyl iodide were added thereinto, and the resulting mixture was heated for 6 hours under refluxing. Thereafter, the reaction mixture was poured into a mixed liquid of 600 ml of water and 350 ml of ethyl acetate, then hydrochloric acid was added thereinto to make the mixture acidic, and concussion and extraction were carried out. The organic layer thus obtained was washed until the washings had reached neutrality, and then the solvent was distilled off. The residue thus obtained was dissolved into 25 ml of methanol and the resulting solution was poured into 1.3 L of water to cause deposition. The deposited product was collected by filtration, and dryed to obtain partially ethyletherified polyvinylphenol having an ethyletherification ratio of 18.8 mole%. Referential Example 2 - 4 Referential Example 1 was repeated except 3.84 g, 3.90 g or 2.96 g of ethyl iodide was used instead of 3.38 g of ethyl iodide used in Referential Example 1 to obtain partially ethyletherified polyvinylphenol having an ethyletherification ratio of 20.3 mole%, 21.8 mole% or 16.7 mole%, respectively. Example 1 Into 48 parts of diethyleneglycol dimethylether, 13.5 parts of partially ethyletherified polyvinylphenol obtained in Referential Example 1, 1.0 part of hexamethylolmelaminehexamethylether (cross-linking agent) and 1.0 part of N-hydroxysuccinimide methanesulfonicacid ester (photo-induced acid precursor) were dissolved. The resulting solution was filtered through a Teflon filter having a pore size of 0.1 µm to prepare a resist solution. A silicon wafer washed in a conventional manner was coated with the resist solution thus prepared by mean of a spinner so as to give a coating thickness of 0.7 µm. Then the silicone wafer was prebaked on a hotplate at 100°C for 1 minute. The prebaked coating film was exposed to light through a patterned chrome mask with KrF Excimer Laser Stepper (NSR-1755, EX8A, NA=0.45, manufactured by Nicon Co.) using 248 nm ultraviolet ray. After the exposure, the wafer was heated on a hot plate at 100°C for 1 minute to cause cross-linking reaction at the exposed part. Thereafter, the wafer was developed with a 2.38 % aqueous solution of tetramethylammonium hydroxide to form a negative pattern. Then, the pattern thus formed was observed by means of electron microscope. The observation revealed that 0.25 µm of the fine line-and-space pattern could be resolved at the exposure dose of 42mJ/cm 2 (248 nm, effective sensitivity) with a good profile and no scam was observed at the unexposed part. Example 2 Example 1 was repeated except that partially ethyletherified polyvinylphenol obtained in Referential Example 2 was used instead of the partially ethyletherified polyvinylphenol obtained in Referential Example 1 to obtain a negative pattern. The pattern thus formed was observed by means of electron microscope and it was revealed that 0.25 µm of the line-and-space pattern could be resolved at the exposure dose of 25mJ/cm 2 (248 nm). Example 3 Example 1 was repeated except that partially ethyletherified polyvinylphenol obtained in Referential Example 3 was used instead of the partially ethyletherified polyvinylphenol obtained in Referential Example 1 to obtain a negative pattern. The pattern thus formed was observed by means of electron microscope and it was revealed that 0.25 µm of the line-and-space pattern could be resolved at the exposure dose of 20mJ/cm 2 (248 nm). Example 4 Example 1 was repeated except that partially ethyletherified polyvinylphenol obtained in Referential Example 4 was used instead of the partially ethyletherified polyvinylphenol obtained in Referential Example 1 to obtain a negative pattern. The pattern thus formed was observed by means of electron microscope and it was revealed that 0.25 µm of the line-and-space pattern could be resolved at the exposure dose of 29mJ/cm 2 (248 nm). Example 5 Example 1 was repeated except that, as the alkali-soluble resin, the mixture of 8.1 parts of partially ethyletherified polyvinylphenol obtained in Referential Example 2 and 5.4 parts of copolymer of vinylphenol and styrene (LYNCUR CST-70; weight average molecular weight 1720; molar ratio of vinylphenol to styrene is 70 : 30 ; manufactured by Maruzen Petrochemical Co.) was used instead of the partially ethyletherified polyvinylphenol obtained in Referential Example 1 to obtain a negative pattern. The pattern thus formed was observed by means of electron microscope and it was revealed that 0.25 µm of the line-and-space pattern could be resolved at the exposure dose of 27mJ/cm 2 (248 nm). Comparative Example 1 According to the same manner as in Example 1 except that 13.5 parts of polyvinylphenol was used instead of the partially ethyletherified polyvinylphenol obtained in Referential Example 1, a resist solution was prepared. A silicon wafer washed in the conventional manner was coated with the resist solution by means of a spinner so as to give a coating thickness of 0.7 µm. Then the silicone wafer was prebaked on a hotplate at 100°C for 1 minute. The prebaked coating film was exposed to light through a patterned chrome mask with KrF Excimer Laser Stepper (NSR-1755, EX8A, NA=0.45, manufactured by Nicon Co.) using 248 nm ultraviolet ray. After the exposure, the wafer was heated on a hot plate at 105°C for 1 minute to cause cross-linking reaction at the exposed part. Thereafter, the wafer was developed with a 2.0% aqueous solution of tetramethylammonium hydroxide to form a negative pattern. Then, the pattern thus formed was observed by means of electron microscope and it was revealed that only 0.35 µm of the line-and-space pattern could be resolved at the exposure dose of 50mJ/cm 2 (248 nm). Referential Example 5 Into acetone, 10 g of hydrogenated polyvinylphenol (LYNCUR PHM-C; weight average molecular weight 5400; manufactured by Maruzen Petrochemical Co.) was dissolved, then 12.0 g of potassium carbonate and 1.95 g of ethyl iodide were added thereinto, and the resulting mixture was heated for 6 hours under refluxing. Thereafter, the reaction mixture was poured into 2000 ml of pH 3 aqueous solution of acetic acid to cause deposition. Then, deposited resin was collected by filtration and dryed. The resin thus obtained was dissolved into acetone so that its concentration came to 20 %. Then the resulting solution was mixed with hexane (the mixing ratio is 2 : 1 by weight), stirred for 1 hour at room temperature and left for a while. Then the acetone layer was separated and poured into 2000 ml of ion exchanged water to cause deposition. The deposited product was collected by filtration, and dryed to obtain partially ethyletherified hydrogenated polyvinylphenol having the ethyletherification ratio of 15 mole%. Referential Example 6 Referential Example 5 was repeated except 1.56 g of ethyl iodide was used instead of 1.95 g of ethyl iodide to obtain partially hydrogenated ethyletherified polyvinylphenol having the etyletherification ratio of 12 mole%. Example 6 Into 48 parts of diethyleneglycol dimethylether, 13.5 parts of partially ethyletherified hydrogenated polyvinylphenol obtained in Referential Example 5, 1.0 part of hexamethylolmelaminehexamethylether (cross-linking agent) and 1.0 part of N-hydroxysuccinimide methanesulfonicacid ester (photo-induced acid precursor) were dissolved. The resulting solution was filtered through a Teflon filter having a pore size of 0.1 µm to prepare a resist solution. A silicon wafer washed in a conventional manner was coated with the resist solution thus prepared by means of a spinner so as to give a coating thickness of 0.7 µm. Then the silicone wafer was prebaked on a hot plate at 100°C for 1 minute. The prebaked coating film was exposed to light through a patterned chrome mask with KrF Excimer Laser Stepper (NSR-1755, EX8A, NA=0.45, manufactured by Nicon Co.) using 248 nm ultraviolet ray. After the exposure, the wafer was heated on a hot plate at 100°C for 1 minute to cause cross-linking reaction at the exposed part. Thereafter, the wafer was developed with a 2.38% aqueous solution of tetramethylammonium hydroxide to form a negative pattern. Then, the pattern thus formed was observed by means of electron microscope. The observation revealed that 0.25 µm of the fine line-and-space pattern could be resolved at the exposure dose of 25 mJ/cm 2 (248 nm) with a good profile and no scam was observed at the unexposed part. Example 7 Into 60 parts of propyleneglycol monomethylether acetate, 6.75 parts of partially ethyletherified hydrogenated polyvinylphenol obtained in Referential Example 5, 6.75 parts of partially ethyletherified polyvinylphenol (ethyletherification ratio is 22 %), 1.0 part of hexamethylolmelaminehexamethylether (cross-linking agent) and 0.75 part of N-hydroxysuccinimideethane sulfonic acid ester (photo-induced acid precursor) were dissolved. Thereafter, same processes as in Example 6 were conducted, except that the temperature for heating the wafer after the exposure was altered to 110°C, to form a negative pattern. Then, the pattern thus formed was observed by means of electron microscope. The observation revealed that 0.25 µm of the fine line-and-space pattern could be resolved at the exposure dose of 13 mJ/cm 2 (248 nm) with a good profile and no scam was observed at the unexposed part. Example 8 Into 60 parts of propyleneglycol monomethylether acetate, 10.8 parts of partially ethyletherified hydrogenated polyvinylphenol obtained in Referential Example 6, 2.7 parts of partially ethyletherified polyvinylphenol (ethyletherification ratio is 22 % ), 1.0 part of hexamethylolmelaminehexamethylether (cross-linking agent) and 0.75 part of N-hydroxysuccinimide ethanesulfonicacid ester (photo-induced acid precursor) were dissolved. Thereafter, same processes as in Example 7 were conducted to form a negative pattern. Then, the pattern thus formed was observed by means of electron microscope. The observation revealed that 0.25 µm of the fine line-and-space pattern could be resolved at the exposure dose of 20 mJ/cm 2 (248 nm) with a good profile and no scam was observed at the unexposed part.

Claims: A negative photoresist composition which comprises; (A) an alkali soluble resin containing at least one resin selected from the group consisting of a partially alkyletherified polyvinylphenol and a partially alkyletherified hydrogenated polyvinylphenol; (B) a photo-induced acid precursor containing at least a kind of sulfonic acid esters of N-hydroxyimide compounds; and (C) a cross-linking agent. The photoresist composition according to claim 1, wherein the alkali soluble resin is a partially alkyletherified poly(p-vinylphenol) having an alkyletherification ratio of from 10 to 35%. The photoresist composition according to claim 1, wherein the alkali soluble resin is a partially alkyletherified hydrogenated polyvinylphenol having an alkyletherification ratio of from 5 to 30%. The photoresist composition according to any of claims 1 to 3, wherein the sulfonic acid ester of N-hydroxyimide compound is a compound represented by the following formula (I); wherein R 1 is an optionally substituted arylene, alkylene or alkenylene group and R 2 is an optionally substituted alkyl or aryl group. The photoresist composition according to claim 4, wherein R 2 is an optionally substituted alkyl or aryl group, provided that when R 2 is a substituted alkyl or aryl group, its substituent is not a fluorine atom.

Inventors: KUSUMOTO TAKEHIRO, NAKANO YUKO, OKA HIROMI, TAKEYAMA NAOKI, UEDA YUJI, KUSUMOTO, TAKEHIRO, NAKANO, YUKO, OKA, HIROMI, TAKEYAMA, NAOKI, UEDA, YUJI
Applicants: SUMITOMO CHEMICAL CO, SUMITOMO CHEMICAL COMPANY LIMITED
Application year: 1994
Main classification: G03F7
IPC codes: G03F7